Electrolyser

ABSTRACT

An electrolyser comprising a stack of electrolysis plates, the plates being maintained in substantial alignment to comprise an electrolysis cell, and a press for applying a compressive force to opposed ends of the cell whereby the press maintains the electrolysis plates in substantial alignment when the electrolyser is in operation.

FIELD OF THE INVENTION

This invention relates to an assembly for securing and compressing astack electrolysis cell.

BACKGROUND OF THE INVENTION

Electrolysis cells have long been used to generate hydrogen from water,generally in the form of an electrolyte solution.

In a particular electrolysis cell, porous anode and cathode plates arearranged in a stack with an electrolyte permeable-gas impermeablemembrane placed between each anode and cathode pair (for example asdescribed in PCT Publication No. WO2004/020701 and Canadian PatentApplication No. 2,400,775 ELECTROLYZER, Helmke et al., both of which areincorporated herein by reference). By providing separate channels toeach of the anodes and cathodes, the product gases generated at each ofthe anodes and cathodes may be separately output from the cell.Electrolyte is circulated through the porous anodes and cathodes. Inorder to circulate the electrolyte and provide an outlet for the productgases, the channels are created by cutting holes or slots in each platethat align when the plates are stacked. The aligned holes and slots formthe channels to circulate electrolyte and provide for output of theproduct gases.

An advantageous method of manufacturing such a cell has been to stackthe anode plates, cathode plates and membranes and encase the resultingstack in an electrolyte impermeable-gas impermeable membrane such asepoxy resin. The epoxy is used to assist in sealing the edges of theplates and to secure the plates in an aligned stack. The resultantelectrolyser may thus be comprised of multiple electrolysis cellsencased in an epoxy resin casing. Ports may be provided through theepoxy casing to permit circulation of electrolyte and output of theproduct gases. Electricity may be provided to the cells via anelectrical connection that extends out of the epoxy.

While this method of creating an electrolyser from a stack of anode andcathode plates has been successful, it does suffer from somelimitations. The resulting electrolysers are limited in their gas outputrate as elevated internal pressures cause the epoxy to swell and allowthe plates to separate. Once the plates separate, even by a relativelysmall amount, the channels may no longer be completely separate. Even asmall breakdown in channel integrity may result in co-mingling ofproduct gases and electrolyte, reducing output from the electrolyser.

It would be advantageous to provide for a stack cell and a method ofmanufacturing such a stack cell that alleviates these limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate embodiments of the invention by way ofexample only:

FIG. 1A is an exploded perspective view of a stack of electrolysisplates.

FIG. 1B is a perspective view of the assembled stack of electrolysisplates of FIG. 1 a.

FIG. 2 perspective view of an assembled electrolyser according to anembodiment of the invention.

FIG. 3 is a cross-sectional elevation of the electrolyser of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides an electrolyser comprising a stack ofelectrolysis plates, the plates being maintained in substantiallyparallel alignment, and a press for applying a compressive forcetransversely to the stack, to compress the stack between opposed facesof the cell, the press comprising a front face, a compression supportplate fixed in position relative to the front face and spaced from thefront face, a moving platen, the stack being disposed between the platenand the front face, and a compression member for applying a compressiveforce to the platen such that the platen applies a transversecompressive force substantially uniformly over a face of the stack,whereby the press maintains the electrolysis plates in substantiallyparallel alignment when the electrolyser is in operation.

In further embodiments of the electrolyser of the invention: Thecompression member comprises a spring bearing against the platen; thespring is actuated by a disk threadedly secured to the compressionsupport plate and bearing against the spring; the spring is disposed ina recess disposed on a face of the platen; the spring surrounds a hubdisposed in the recess; the hub surrounds a key; the front face isformed by a jacket; the front face is formed integrally with side facesof the jacket; and/or the compression support plate is affixed to theside walls.

The invention further provides a method of stabilising an electrolysercomprising a stack of electrolysis plates, the electrolysis plates beingin substantially parallel alignment, the method comprising the steps of:a. locating the stack of electrolysis plates in a press comprising afront face and a compression support plate fixed in position relative tothe front face; and b. rotating a threaded compression member to apply acompressive force to a platen bearing against the stack, such that theplaten applies a transverse compressive force substantially uniformlyover a face of the stack; whereby the press maintains the electrolysisplates in substantially parallel alignment when the electrolyser is inoperation.

FIG. 1A illustrates an exploded view of a stack 10 of electrolysisplates 12 comprising alternating porous anode and cathode plates with anelectrolyte permeable-gas impermeable membrane 12 a between eachanode-cathode pair.

The electrolysis plates 12 may be assembled into the stack 10 havingpositive and negative terminals 11, 13, respectively, as illustrated inFIG. 1B, and encased in a sealant such as epoxy, a silicone compound orany other suitable sealant, to seal the edges of the plates and, inconjunction with the compression member described below, maintain theplates 12 in the stack 10 in precise parallel alignment within theelectrolysis cell 20.

As more fully described in WO2004/020701 and CA2,400,775, which areincorporated herein by reference, slots in the plates align when stackedto form channels through the stack 10. The channels permit circulationof electrolyte through the stack 10 and output of the product gases fromthe cell 20. A first product gas (in the case of the electrolysis cellshown, one of hydrogen and oxygen) is output from one or more first gasoutput ports 22, a second product gas (in the case of the electrolysiscell shown, the other of hydrogen and oxygen) is output from one or moresecond gas output ports 24, electrolyte is input through one or moreelectrolyte input ports 28, and electrolyte is output through a set ofone or more electrolyte output ports 26, as illustrated in FIGS. 1B and2. As will be appreciated, the placement and number of ports may varyfrom the embodiment illustrated in FIGS. 1B and 2. Also shown is anoutput 29 for a thermocouple, for monitoring the temperature of theelectrolysis cell 20.

During operation of the cell 20, a current supplied to electrodes 11, 13results in hydrogen and oxygen gas being generated in the electrolysisplates 12 of the cell 20. The generation of these product gasesincreases the internal pressure of the cell 20, causing the productgases to egress through the first and second product gas ports 22, 24.In order to increase the gas output of the cell 20, a higher electricalinput may be supplied to the electrodes 11, 13. The higher electricalinput results in the product gases being generated more quickly, theinternal pressure of the cell 20 increasing and a higher flow rate ofproduct gases from product gas ports 22, 24.

However, the higher electrical input increases the temperature of thestack 10 with attendant increased thermal expansion of the stack 10. Anyseparation of the plates 12 within the stack 10 (either by spreading orby loss of parallel alignment) consequent to thermal expansion causesloss of output gases and therefore reduces the efficiency of the cell20.

It has been found that the electrolysis cell 20 may be operated athigher levels of gas output, and consequent higher internal operatingpressures, if a substantially even compressive force is applied toopposite faces of the cell 20 and maintained during operation. In thepreferred embodiment the compression member accommodates thermalexpansion of the encased stack 10 while under the compressive force.

In the embodiment illustrated, the invention provides a press forsecuring the electrolyser containing the stack 10 of electrolysis plates12, comprising a compression plate for compressing the encased stack 10against the jacket 30 of the cell 20, and a disk spring 50 which can beadjusted to set a rest compression and which allows the compressionplate to move as the stack 10 expands while maintaining a relativelyconstant pressure against the encased stack 10 as the cell 20 heats up.

As illustrated in FIGS. 2 and 3, the stack 10 is contained within ajacket 30 constructed of a sturdy, rigid material such as stainlesssteel, carbon fibre, plastic (for example polyetheretherketon (PEEK),PVC, CPVC), or other suitable material. As shown the jacket 30 is bentto form the front face 30 a and sides 30 b, however these may be formedas separate components if desired. The electrodes 11, 13 protrudethrough one end plate 30 c and another end plate 30 d seals the oppositeend of the cell 20. The ends 30 c, 30 d may be bolted or otherwisesuitably affixed to the front face and sides 30 a, 30 b of the jacket30.

A compression platen 32 is movably disposed opposite to the face 30 a,preferably nested within the jacket 30 as shown in FIG. 3. Thecompression platen 32 is similarly formed from a sturdy, rigid materialand spans the length and width of the stack 10.

A compression member comprising a disk spring 50 is disposed generallycentrally along the platen 32, for applying a compressive force to thestack 10. The disk spring 50 may be mounted in a recess 32 a in theouter face of the platen 32, and surrounds a hub 52 and key 54 whichinterlocks with a rotatable disk 56 threadedly engaged to an opening 42through a compression support plate 40, the hub 52 maintaining thespring 50 in axial alignment beneath the disk 56.

The compression support plate 40 is in turn bolted to the jacket 30 (asseen in FIG. 2). The compression support plate 40 and jacket 30 thusform a press frame containing disk spring 50 in contact with movingplaten 32.

Optionally an elastomer layer 46 may be positioned between the stack 10and the face 30 a of the electrolysis cell 20, serving as a thermalinsulator and allow for any imperfections between face 30 a and thefacing side of the electrolysis cell 20. The elastomer layer 46 may forexample be composed of Ethylene Propylene Dieene Monomer, but anysuitable thermal insulating material may be used if desired.

The cell 20 is assembled by inserting the encased stack 10 into thejacket (after inserting a thermally insulating layer 46, if desired),and inserting the platen 32 over the stack 10. The disk spring 50 ismounted in the recess 32 a about the hub 52 and key 54, and the supportplate 40 (with disk 56 threaded into opening 42) is bolted to the jacket30.

After assembly of the cell 20, the disk 56 can be tightened to a desiredtorque, forcing platen 32 toward stack 10 and thus applying a uniformcompression over the face of the stack 10 (the opposite face of thestack 10 bearing against the interior of face 30 a of jacket 30,applying a uniform compression over the opposite face of the stack 10).This manner of compression is superior to conventional compression meanssuch as corner bolts, because a single member can be adjusted to applyeven compression over the entire face of the stack. Moreover, even ifcorner bolts could be tightened to supply an initial uniformcompression, through constant expansion and contraction the compressionwill eventually become non-uniform and allow the plates 12 to come outof parallel alignment. Even the slightest loss of parallel alignmentbetween the plates 12 will result in reduced efficiency of the cell 20,and substantial loss of parallel alignment will result in catastrophicfailure of the cell 20.

In operation, as described in WO2004/020701 and CA2,400,775, which areincorporated herein by reference, slots in the plates 12 form channels(not shown) through the stack 10 which permit circulation of electrolytethrough the stack 10 and output of the product gases from the cell 20. Acurrent supplied to electrodes 11, 13 results in hydrogen and oxygen gasbeing generated in the electrolysis plates 12 of the cell 20 viaelectrolysis, as is well known. The generation of the product gasesincreases the internal pressure of the cell 20, causing the productgases to egress through the first and second product gas ports 22, 24.In the case of the electrolysis cell shown, hydrogen is output fromfirst gas output port 22, and oxygen is output from second gas outputport 24. Electrolyte is circulated through input port 28 and output port26, ensuring a constant supply of electrolyte solution.

Increasing the electrical input results in the product gases beinggenerated more quickly, the internal pressure of the cell 20 increasingand a higher flow rate of product gases from product gas ports 22, 24.However, it also results in greater thermal expansion of the stack 10.As the stack 10 expands transversely (relative to the plane parallel tothe plates 12) the disk spring 50 yields to maintain a substantiallyconstant compression against the stack 10. This not only preventsmisalignment of the plates 12, but also reduces the risk of cracking ofthe epoxy encasement material. The compression remains uniform, becausethe pressure from disc spring 50 is applied generally centrally to theplaten 32 over the area of the disk spring 50.

Various embodiments of the present invention having been thus describedin detail by way of example, it will be apparent to those skilled in theart that variations and modifications may be made without departing fromthe invention. The invention includes all such variations andmodifications.

1. An electrolyser, comprising a stack of electrolysis plates, theplates being maintained in substantially parallel alignment, and a pressfor applying a compressive force transversely to the stack, to compressthe stack between opposed faces of the cell, the press comprising afront face, a compression support plate fixed in position relative tothe front face and spaced from the front face, a moving platen, thestack being disposed between the platen and the front face, and acompression member for applying a compressive force to the platen suchthat the platen applies a transverse compressive force substantiallyuniformly over a face of the stack, whereby the press maintains theelectrolysis plates in substantially parallel alignment when theelectrolyser is in operation.
 2. The electrolyser of claim 1 wherein thecompression member comprises a spring bearing against the platen.
 3. Theelectrolyser of claim 2 wherein the spring is actuated by a diskthreadedly secured to the compression support plate and bearing againstthe spring.
 4. The electrolyser of claim 2 wherein the spring isdisposed in a recess disposed on a face of the platen.
 5. Theelectrolyser of claim 4 wherein the spring surrounds a hub disposed inthe recess.
 6. The electrolyser of claim 5 wherein the hub surrounds akey.
 7. The electrolyser of claim 1 wherein the front face is formed bya jacket.
 8. The electrolyser of claim 7 wherein the front face isformed integrally with side faces of the jacket.
 9. The electrolyser ofclaim 8 wherein the compression support plate is affixed to the sidewalls.
 10. A method of stabilising an electrolyser comprising a stack ofelectrolysis plates, the electrolysis plates being in substantiallyparallel alignment, the method comprising the steps of: a. locating thestack of electrolysis plates in a press comprising a front face and acompression support plate fixed in position relative to the front face;and b. rotating a threaded compression member to apply a compressiveforce to a platen bearing against the stack, such that the platenapplies a transverse compressive force substantially uniformly over aface of the stack; whereby the press maintains the electrolysis platesin substantially parallel alignment when the electrolyser is inoperation.
 11. The method of claim 10 wherein in step b. the compressiveforce is applied to the platen generally centrally.